Brake pressure control valve

ABSTRACT

The invention relates to a brake pressure control valve which contains a brake pressure build-up valve. The brake pressure build-up valve comprises a pressure compensated seat valve. A second valve member, a rod between the two valve members and a tubular compensating piston are provided to produce pressure compensation at the valve member. The compensating piston which encloses the rod is displaceable relative to the latter and comprises a second valve seat at its end directed towards the second valve member. A sealing ring also encloses the tubular compensating piston. When the first valve member is raised from its valve seat, the second valve member can precede the tubular compensating piston, thereby preventing friction forces between this compensating piston and its sealing ring from being disruptive during opening of the seat valve. Also provided is a valve slide which only uncovers flow bores when the seat valve is opened for the purpose of increasing brake pressure. Brake pressures can be smoothly controlled by means of the control slide.

BACKGROUND OF THE INVENTION

The invention relates to a brake pressure control valve as definedhereinafter. SAE paper 840 465 discloses a brake pressure control valvewhich incorporates both a brake pressure reduction valve and a pressurebuild-up valve. The brake pressure build-up valve comprises a valvechamber which has an inner valve seat and which is designed forconnection to a pressure source, a valve member which is movable in thevalve chamber and which is at least partially spherical in shape, acompensating piston coupled to the valve member and a seal which sealsthe compensating piston relative to the valve chamber and also a closingspring. The compensating piston and the valve member are oppositelyinfluenced by the pressure from the pressure source and thus relativelyminor force is required to raise the valve member from the valve seat.The disadvantage is that as the valve member is being raised from andmoved back to this valve seat friction forces are produced between thecompensation piston and its seal. These friction forces impede thesmooth raising and lowering of the valve member and accordingly thesmooth apportioning of brake pressures. Smooth apportioning of brakepressures is further impeded in that even minor lifting of the valvemember results in large valve opening cross-sections.

OBJECT AND SUMMARY OF THE INVENTION

The advantage of this invention over the prior art is that no disruptivefriction forces are produced at the pressure build-up valve while thevalve member is being raised from its valve seat.

The measures described herein represent advantageous developments of andimprovements to the brake pressure control valve described in thisapplication.

A further advantage of this invention is that the brake pressure controlvalve may be inexpensively produced.

Another advantage of the invention is to provide an improved seal.

Yet another feature of this invention is to facilitate smootherapportioning of brake pressures.

Further revelations of this invention can also be implemented withoutthe utilization of each and every feature disclosed.

Additional advantages revealed herein are the use of individualconstruction features such as providing bores which extend through thecontrol slide as well as a longitudinal groove being incorporated in thecylindrical bore.

The invention will be better understood and further objects andadvantages thereof will become more apparent from the ensuing detaileddescription of a preferred embodiment taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross sectional view of a first embodiment,

FIG. 2 is a cross-sectional view of an individual feature of a secondembodiment of the invention, and,

FIG. 3 shows in a cross sectional view a third embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The brake pressure control valve shown in FIG. 1 is housed in a housing3. The housing may possibly also contain a braking force amplifier (notshown) and be directly connected to a wheel brake 4. For this purposethe housing 3 is provided with a connection bore 5. Another connectionbore 6 is connected to a pressure source 7. This pressure source 7 canbe of the state of the art and comprises at least a pump 8 and apressure storage element 9. Another connection bore 10 is connected to apressure medium storage container 11 from which the pressure source 7 issupplied.

The housing 3 has a stepped bore 12 which receives the brake pressurecontrol valve 2. The brake pressure control valve 2 comprises a firstsleeve-like component 13, which receives a second sleeve-like component14 and a third component 15. At one end, the sleeve-like component 13has a coaxially oriented cylindrical bore 16 and at least one controlbore 17 disposed at right angles thereto, thereby forming a rigidcontrol sleeve. A control slider 18 is displaceable in the bore 16. Thecontrol slider 18 has a control edge 19. The control slider 18 can bemoved by means of a brake pedal (not shown) via a path simulator spring20 (shown) so that its control edge 19 passes the control bores 17 andthe control slider 18 thereby closes these control bores 17. When thecontrol slider 18 is moved from the locking position described, backinto the starting position shown, the control bores 17 are partiallyfreed. As a result, connections are thereby produced between thecylindrical bore 16 and the control bores 17 which in turn communicatewith the connection bore 10 via connection channels 21. Accordingly,when the control slider 18 is in the position indicated there exists apressure medium outflow path to the pressure medium storage container11. Thus, in the region of the cylindrical bore 16, the component 13together with the control slide 18, forms a pressure reduction valve 22.

Adjacent to the cylindrical bore 16 the component 13 comprises anotherbore 23 which has a larger diameter and to which the bores 24 and 25with even larger diameters are connected. The component 14 has two outerdiameters which are adapted to the diameters of the bores 23 and 24. Inthe region of transition of the diameters there is an annular area 26between the component 13 and component 14. Flow bores 27 which dischargeinto an annular area 28 disposed between the component 13 and thehousing 3 extend radially outwards from the annular area 26. The annulararea 28 communicates with the connection bore 6. Additional flow bores29 extending inwardly in a radial direction pass from the annular area26 through the component 14.

In the region of these flow bores 29 and in a similar axial orientationto the cylindrical bore 16, the component 14 comprises a cylindricalbore 30 such that in the region of this cylindrical bore 30 thecomponent 14 forms a fixed control sleeve. Adjacent to the cylindricalbore 30 is the direction of the cylindrical bore 16 the component 14comprises a first valve seat 31 and thereby forms a valve chamber. Astepped bore 32, which is open to the cylindrical bore 16, connects tothe valve seat 31. This stepped bore 32 communicates with the bore 25via at least one of the radial bores 33 extending through the component14 and one of the radial bores 34, 35 which extends through component13. At least one bore 36 which communicates with the connection bore 5via an annular area 37 disposed between component 13 and the housing 3extends in a radial direction from the bore 25. A first valve member 38is provided for the valve seat 31. This member consists, for example, ofa ball. A control lug 39 is provided on the control slide 18 and extendsin the direction of the ball. The length of the control lug 39 iscalculated such that when the control slide 18 is moved in the directionof the ball 38 the control lug 39 only closes the control bore 17 whenpartial chambers disposed within the bore 30 and connected by acompensating channel 41 are hydraulically relieved when the ball 38 isslightly raised from its valve seat 31. A cylindrical control slide 40is united to the ball 38. When the ball 38 has opened its valve seat 31this control slide 40 still closes the flow bores 29. These flow bores29 are advantageously so oriented with respect to the cylindrical bore30 that during operation virtually no disruptive radial forces influencethe cylindrical control slide 40. In the case of the present embodimentthis is achieved in that the bores 29 lie on a common axis which passesthrough the longitudinal axis of the cylindrical bore 30. The controlslide 40 contains at least the one pressure compensating channel 41.Accordingly, as indicated, the partial chambers located on each side ofthe control slide 40 within the cylindrical bore 30 communicate with oneanother.

On the same axis as the first valve seat 31 there is provided a tubularcompensating piston 42 which is spaced apart from the control slide 40and which is movable with respect thereto. This compensating piston 42projects out of the component 14 and is there provided with a secondvalve seat 43. A second valve member 44 is provided for this valve seat43. This second valve member 44 is also in the form of a ball and isconnected to the first valve member 38 via a rod 45 which extendsthrough the tubular compensating piston 42, preferably with minimalradial play. The connection may be effected, for example, by means ofelectrical butt welding. Concentrical recesses 46--46 may be provided onboth ends of the rod 45 for the purpose of orienting the two balls 38and 44 relative to the rod 45. The control slide 40 may be connected tothe ball 38, for example, by butt welding or, alternatively, it may bepressed against the ball 38 by means of a spring (not shown).

To ensure accurate coaxial alignment of the two balls 38 and 44 and ofthe periphery of the cylindrical control slide 40, the periphery can befinished by grinding after being welded to the other components. Thecomponent 14 has incorporated therein a sealing ring 47 which enclosesthe compensating piston 42 in a seal-tight manner such that uponovercoming the friction forces the compensating piston is longitudinallydisplaceable. A rigidly disposed ring 48 holds the sealing ring 47 inthe component 14. A closing spring 49 presses against the second valvemember 44 in the direction of the first valve seat 31 with aself-centering pressure piece 50 interpositioned therebetween. Theclosing spring 49 rests on the component 15 which is provided for thispurpose with a pocket bore 51 designed to receive the closing spring 49,the pressure piece 50, the second valve member 44 and a portion of thecompensating piston 42. The component 15 in turn rests on the component13 via a retaining ring 52. Radial bores 53 which open into the bore 25of the component 13 extend from the pocket bore 51 and thereby connectthe pocket bore 51 to the connection bore 5.

The component 14 with the first valve seat 31, the first valve member38, the rod 45, the second valve member 44 and the compensating piston42 and also the second valve seat 43 and the seal 47 form a brakepressure build-up valve 54. With the addition of the control slide 40this brake pressure build-up valve 54 constitutes a slide-controlledseat valve which, as is known, does not have any leakage in the closedstate. The pressure from the pressure source 7 which is graduallycommunicated to the bore 30 through flow bores 27 and 28 and throughunavoidable gaps between the cylindrical bore 30 and the cylindricalcontrol slide 40, produces an essentially axial force compensation atthe valve members 38 and 44 when the brake pressure build-up valve 54 isclosed as a result of the essentially similar diameter of the valve seat31 and the tubular compensating piston 42. In the course thereof thetubular compensating piston 42 is acted on in the direction of thesecond valve member 44 disposed without the cylindrical bore 30. As aresult, the second valve seat 43 is pressed in a seal-tight manneragainst the second valve member 44 by the tubular compensating piston42. In the course thereof, a frictional force of the sealing ring 47 isovercome. Only minimal forces transmissible by the control lug 39 to thefirst valve member 38 are required to raise this valve member 38 fromits valve seat 31. As indicated, pressure compensation is alwaysobtained between one portion of the cylindrical bore 30 and the otherportion as a result of the configuration of the control slide 40 whichcomprises at least one pressure compensating channel 41. As the firstvalve member 38 is raised from its valve seat 31 the second valve member44 is also raised via the rod 45. In this movement the second valvemember 44 precedes the compensating piston 42 in the direction of theclosing spring 49; the compensating piston 42 being slowed down by theseal 47. The advantage of this configuration of the brake pressurebuildup valve according to the invention is that minor force is requiredto open the brake pressure build-up valve. This is advantageous in termsof the smooth opening of the valve seats 31 and 43 since initialbreak-away forces needed to displace the compensating piston 42 do notdisrupt the opening.

Upon actuation of the control slide 18 by a force applied by thesimulator spring 20, the valve element (ball) 38 is moved away from thevalve seat 31. At the same time, the second valve element (ball) 44 thatis firmly joined to the rod 45 is moved counter to the force of theclosing spring 49. As a consequence, a briefly existing pressure excesson the end face of compensation piston 42 disposed in the axialdirection moves the compensation piston 42 by a small amount, out of thespace surrounded by the cylinder bore 30 into the space surrounded bythe bore 51, in the direction of the valve element (ball) 44, butwithout touching the valve element (ball) 44.

During this process, the second valve element (ball) 44 moves away,spaced sufficiently far apart, from the valve seat 43 of thecompensation piston 42, because the control slide 40 is moved by thecontrol slide 18 and ball 38 into the brake pressure control valve 2 toopen bore 29 to the pressure source for the purpose of pressure buildupin the brake system.

The resultant spacing, in the regulated state, between the second valveelement (ball) 44 and the compensation piston 42, assures that the rod45 can be actuated virtually without friction in the compensation piston42, and the valve slide 40 can be actuated virtually without friction inthe bore 30, and that a frictional force of the sealing element thatmust be overcome in the event of possible displacement of thecompensation piston 42 does not become operative at the rod 45.

The cross-section of the tubular compensating piston 42 and the radialplay between this piston and the rod 45 are so calculated that wheninfluenced by pressure from the pressure source a pressure drop may beproduced between the bore 30 and the valve seat 43 with the consequentdisplacement of the compensating piston 42 relative to the seal 47. Whenthe brake pressure build-up valve 54 is later closed this displacementproduces reliable seal-contact between the valve member 44 and its valveseat 43. In summary, the above-described configuration of the brakepressure build-up valve can also be characterized in that it consists increating a force-compensated slide valve with a double valve seat sealwherein one of the valve seats is self-regulating. After the first valvemember 38 has been raised from its valve seat 31 the control slide 40advances in the direction of the seal 47 until it finally graduallyuncovers the flow bores 29. In the course thereof, the brake pressurebuild-up valve 54 operates in the manner of a pressure-compensated slidevalve which can be used in the known manner for the smooth regulation ofpressure medium flows while employing only minimal control force. Itshould be added that the described combination of the first valve member38 and its valve seat 31 and the cylindrical control slide 40 with theassociated cylindrical bore 30 and the flow bores 29 is not limited tothe use of the described tubular compensating piston 42 and itsassociated second valve member 44 and second valve seat 43.

The second valve element ball 44 serves to prevent leakage between therod 45 and the compensation piston 42 in the non-braking position andthe compensation piston lags 44, in order to release the pressurebuildup between control slide 40 and the compensation piston.

In FIG. 2, which shows a section of an embodiment 2a, there isrepresented a component 14a which differs from component 14 shown inFIG. 1 in that longitudinal grooves 55 extend from its cylindrical bore30. These longitudinal grooves 55 replace the pressure-compensatingchannels 41 of the control slide 40. As a result, in the embodiment 2aof FIG. 2, it is possible to employ a control slide 40a which does nothave any breaks. Further ways of providing pressure compensation betweenthe two slides of the control slide 40a consist in providing channelswhich extend through the component 14 (not shown).

The embodiment 2b shown in FIG. 3 differs from the one described firstin that the compensating piston 42b is provided with a flange 57 in theproximity of its valve seat 43 and in that a spring 56 or other flexibleelement is incorporated between the flange 57 and the sealing ring 47.The spring 56 acts on the flange 57 and in the course thereof issupported on a ring 48b which retains the sealing ring 47 in an axialdirection. When the brake pressure build-up valve 54b is closed, theflange 57 is axially spaced apart from a front face 58 of the component13 which forms a stop for the flange 57 when the brake pressure build-upvalve 54b is opened. After the valve 54b is opened this spring 56 pushesthe compensating piston 42 and the valve seat 43 a short distance in thedirection of the valve member 44. As a result, when the brake pressurebuild-up valve 54b is closed the valve member 44 encounters its valveseat 43 before the valve member 38 touches its valve seat 31 with theresulting advantage that seal-tight closure of the brake pressurebuild-up valve 54b is reliably obtained.

The flange 57 may be formed on the compensating piston 42b or,alternatively, as shown in FIG. 3, it may consist of a plate in the formof an elastically expandable retaining ring which is inserted in acircumferential groove 60 provided on the compensating piston 42b.

As indicated in the introduction, the use of balls as valve members 38and 44 allows for the inexpensive production of the brake pressurebuild-up valve 54. These valve members can obviously also be replaced bydifferently formed valve members. For example, the first valve member38, the control slide 40 and the rod 45 can be produced as a singlepiece. It would then merely be necessary to attach the second valvemember 44 to the rod 45 after mounting the compensating piston 42.

The foregoing relates to a preferred exemplary embodiment of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed and desired to be secured by Letters Patent of theUnited States:
 1. A brake pressure control valve comprising a brakepressure build-up valve having a valve chamber (30) with a first innervalve seat (31), a fluid pressure source connectable to said valvechamber, a movable first valve member in said valve chamber forcooperation with said valve seat, a movable compensating piston (42,42b) associated with said first valve member, a sealing ring (47)surrounding said compensating piston and arranged to enclose a portionof said compensating piston in a seal-tight manner, said compensatingpiston (42, 42b) further including an end means arranged to project fromsaid valve chamber, said end means adapted to form a second valve seat,a second valve member arranged to cooperate with said second valve seat,said second valve member being connected to said first valve member viaa rod which extends through said compensating piston with minimal radialplay and a closing spring for closing said first and second valvemembers, a relatively movable control slide having opposite sidesdisposed between said compensating piston and said first valve member,said control slide being connected to said first valve member, saidvalve chamber further provided with a cylindrical bore in proximity tosaid control slide and adapted for enclosure thereof and to thereby forma fixed control valve sleeve; said control slide and said control valvesleeve comprises flow bores adapted to form a control valve which may beopened after the first valve member has been removed from said firstvalve seat, and further wherein at least one pressure compensatingchannel is provided which produces pressure compensating between saidopposite sides of said control slide.
 2. A brake pressure control valveas claimed in claim 1, in which said at least one pressure compensatingchannel comprises a bore which extends through said control slide.
 3. Abrake control valve as claimed in claim 1, in which said at least onepressure conpensating channel comprises a longitudinal grooveincorporated in said cylindrical bore.
 4. A brake pressure control valvecomprising a brake pressure build-up valve having a valve chamber (30)with a first inner valve seat (31), a fluid pressure source connectableto said valve chamber, a movable valve member in said valve chamber forcooperation with said valve seat, a movable compensating piston (42,42b) associated with said valve member, a sealing ring (47) surroundingsaid compensating piston and arranged to enclose a portion of saidcompensating piston in a seal-tight manner, said compensating piston(42, 42b) further including an end means arranged to project from saidvalve chamber, said end means adapted to form a second valve seat, asecond valve member arranged to cooperate with said second valve seat,said second valve member being connected to said first valve member viaa rod which extends through said compensating piston with minimal radialplay and a closing spring for closing said first and second valvemembers, said first and second valve members comprise ball members whichare attached to said rod, a relatively movable control slide havingopposite sides is disposed between said compensating piston and saidfirst valve member, said control slide being connected to said firstvalve member, said valve chamber further provided with a cylindricalbore in proximity to said control slide and adapted for enclosurethereof and to thereby form a fixed control valve sleeve; said controlslide and said control valve sleeve comprises flow bores adapted to forma control valve which may be opened after the first valve member hasbeen removed from said first valve seat, and further wherein at leastone pressure compensating channel is provided which produces pressurecompensation between said opposite sides of said control slide.
 5. Abrake pressure control valve comprising a brake pressure build-up valvehaving a valve chamber (30) with a first inner valve seat (31), a fluidpressure source connectable to said valve chamber, a movable valvemember in said valve chamber for cooperation with said valve seat, amovable compensating piston (42, 42b) associated with said valve member,a sealing ring (47) surrounding said compensating piston and arranged toenclose a portion of said compensating piston in a seal-tight manner,said compensating piston (42, 42b) further including an end meansarranged to project from said valve chamber, said end means adapted toform a second valve seat, said second valve member being connected tosaid first valve member arranged to cooperate with said second valveseat, said second valve member being connected to said first valvemember via a rod which extends through said compensating piston with atight fit and a closing spring for closing said first and second valvemembers, said compensating piston which is displaceable relative to saidsealing ring is influenced by a spring adapted to move said compensatingpiston a specific distance relative to the sealing ring and in thedirection of the second valve member, a relatively movable control slidehaving opposite sides is disposed between said compensating piston andsaid first valve member, said control slide being connected to saidfirst valve member, said valve chamber further provided with acylindrical bore in proximity to said control slide and adapted forenclosure thereof and to thereby form a fixed control valve sleeve; saidcontrol slide and said control valve sleeve comprises flow bores adaptedto form a control valve which may be opened after the first valve memberhas been removed from said first valve seat, and further wherein atleast one pressure compensating channel is provided which producespressure compensation between said opposite sides of said control slide.